diff --git a/UPGRADE-3.3.md b/UPGRADE-3.3.md
index cce38f4b00fd1..2253bea93b51d 100644
--- a/UPGRADE-3.3.md
+++ b/UPGRADE-3.3.md
@@ -44,6 +44,9 @@ DependencyInjection
  * The `DefinitionDecorator` class is deprecated and will be removed in 4.0, use
    the `ChildDefinition` class instead.
 
+ * The ``strict`` attribute in service arguments has been deprecated and will be removed in 4.0.
+   The attribute is ignored since 3.0, so you can simply remove it.
+
 EventDispatcher
 ---------------
 
diff --git a/UPGRADE-4.0.md b/UPGRADE-4.0.md
index 4768ba1242a56..1335b0e6e04d3 100644
--- a/UPGRADE-4.0.md
+++ b/UPGRADE-4.0.md
@@ -68,6 +68,9 @@ DependencyInjection
  * Requesting a private service with the `Container::get()` method is no longer
    supported.
 
+ * The ``strict`` attribute in service arguments has been removed.
+   The attribute is ignored since 3.0, so you can simply remove it.
+
 EventDispatcher
 ---------------